Video encoding and decoding method based on entry point information in a slice header, and apparatus using same

ABSTRACT

A video encoding method includes deriving entry point information specifying an entry point of a substream for a picture. The entry point information includes an offset syntax element when the number of the offset syntax elements is larger than 0, where the offset syntax element represents an entry point offset between two entry points. The entry point information includes a length syntax element when the number of the offset syntax elements is larger than 0, where the length syntax element represents a bits length for the offset syntax element. The offset syntax element represents the number of bytes between the two entry points. A value of the length syntax element plus one corresponds to the bits length of the offset syntax element. A value of the number syntax element corresponds to the number of offset syntax elements in the slice header.

This application is a continuation of U.S. patent application Ser. No.15/860,412, filed Jan. 2, 2018, now allowed, which is a continuation ofU.S. patent application Ser. No. 14/369,063, filed Jun. 26, 2014, nowU.S. Pat. No. 9,883,185, which is a National Phase application ofInternational Application No. PCT/KR2012/011717, filed Dec. 28, 2012,and claims the benefit of U.S. Provisional Application Nos. 61/581,105,filed Dec. 29, 2011, 61/582,822, filed Jan. 4, 2012, 61/586,112, filedJan. 12, 2012, and 61/597,145, filed Feb. 9, 2012, all of which arehereby incorporated by reference in their entirety for all purposes asif fully set forth herein.

TECHNICAL FIELD

The present invention relates to a video information compressiontechnique, and more particularly, to a method of signaling a bitstreamincluding video information and a method of parsing information usingthe same.

BACKGROUND ART

Recently, demands for high-resolution and high-quality images haveincreased in various fields of applications. As images have higherresolution and higher quality, the amount of information on the imagesalso increases.

Accordingly, if video data is transmitted media such as existing wiredand wireless broadband lines, or is stored using conventional storagemedia, the costs of transmitting and storing data also rise.

High-efficiency video compression techniques may be employed in order toeffectively transmit, store, and reproduce information in videos withhigh resolution and high quality.

In order to improve video compression efficiency, inter prediction andintra prediction can be used. In inter prediction, pixel values within acurrent picture are predicted by referring to information on anotherpicture. In intra prediction, pixel values within a current picture arepredicted using connections between pixels within the same picture.

A processing unit of a predicted picture, for example, a block, may besubjected to various methods so as to render the picture identical tothe original picture. Accordingly, a decoding apparatus may decode thepicture more exactly to be identical to the original picture, and anencoding apparatus may encode the picture to be reconstructed moreexactly.

DISCLOSURE Technical Problem

An aspect of the present invention is to provide a method and apparatusfor effectively signaling encoded video information.

Another aspect of the present invention is to provide a method andapparatus for setting an entry point in bytes and signaling the entrypoint when parallel decoding is used.

Still another aspect of the present invention is to provide a method andapparatus for performing parallel decoding using a byte-aligned decodingunit.

Yet another aspect of the present invention is to provide a method andapparatus for specifying information transmitted and received forperforming parallel decoding using a byte-aligned decoding unit andperforming encoding and decoding using the information.

Technical Solution

An embodiment of the present invention provides a video encoding methodincluding entropy-encoding quantized transform information andtransmitting the entropy-encoded information in a bitstream, wherein thebitstream comprises information specifying, in bytes, information to besubjected to parallel decoding.

The bitstream may include, in a slice header, offset informationspecifying an entry point of a row of coding tree units (CTUs) to besubjected to parallel decoding, and the offset information may indicatea number of bytes between two entry points.

The entropy-encoding may start entropy-encoding at an access pointindicated by an entry point of a row of CTUs, in which when a referenceCTU of a current row is completely entropy-encoded, entropy-encoding afirst CTU in a next row may start based on context of the reference CTU,a number of bytes of the current row being indicated by an offsetbetween entry points transmitted in the bitstream.

Another embodiment of the present invention provides a video decodingmethod including receiving a bitstream and performing parallel decodingbased on the bitstream, wherein the bitstream comprises informationspecifying, in bytes, information to be subjected to parallel decoding.

The performing of the decoding may include entropy-decoding thebitstream and reconstructing a picture based on entropy-decodedinformation.

reconstructing a picture based on entropy-decoded information.

The performing of the decoding may entropy-decode a L-th CTU CTU_(NL) inan N-th row of CTUs and then entropy-decode a first CTU CTU_(N+11) in an(N+1)-th row of CTUs based on context of the CTU_(ML), N and L being aninteger, in which a number of bytes of the N-th row may be indicated byN-th offset information of information on offsets between entry pointsincluded in the bitstream.

That is, the bitstream may include offset information specifying anentry point of a row of CTUs to be subjected to parallel decoding, andthe offset information may indicate a number of bytes between two entrypoints. The offset information may be transmitted via a slice header.

The performing of the decoding may start decoding at an access pointindicated by an entry point of a row of CTUs, in which when a referenceCTU of a current row is completely entropy-decoded, entropy-decoding afirst CTU in a next row may start based on context of the reference CTU,a number of bytes of the current row being indicated by an offsetbetween entry points transmitted in the bitstream.

Advantageous Effects

According to the present invention, encoded video information iseffectively signaled, thereby improving coding efficiency.

Further, when parallel decoding is used, an entry point is set in bytesand signaled, thereby effectively utilizing data resources andincreasing compression efficiency.

In addition, parallel decoding is carried out using a byte-aligneddecoding unit, thereby remarkably enhancing video decoding efficiency.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram schematically illustrating a video encodingapparatus according to an exemplary embodiment of the present invention.

FIG. 2 is a block diagram schematically illustrating a video decodingapparatus according to an exemplary embodiment of the present invention.

FIG. 3 schematically illustrates a slice according to an exemplaryembodiment.

FIG. 4 schematically illustrates a tile and a slice according to anexemplary embodiment.

FIG. 5 schematically illustrates a tile and a slice according to anotherexemplary embodiment.

FIG. 6 schematically illustrates a WPP substream.

FIG. 7 schematically illustrates a tile.

FIG. 8 schematically illustrates a relationship between WPP and a tile.

FIG. 9 schematically illustrates order of largest coding units (LCUs) ina picture according to an exemplary embodiment.

FIG. 10 schematically illustrates order of LCUs in a bitstream accordingto an exemplary embodiment.

FIG. 11 schematically illustrates byte alignment of a substreamaccording to an exemplary embodiment.

FIG. 12 schematically illustrates an entry point of a WPP substreamaccording to an exemplary embodiment.

FIG. 13 schematically illustrates an entry point of a tile according toan exemplary embodiment.

FIG. 14 schematically illustrates an entry point when a tile and a WPPsubstream are used together according to an exemplary embodiment.

FIG. 15 is a flowchart schematically illustrating an encoding methodaccording to an exemplary embodiment of the present invention.

FIG. 16 is a block diagram schematically illustrating an encodingapparatus according to an exemplary embodiment of the present invention.

FIG. 17 is a flowchart schematically illustrating a decoding methodaccording to an exemplary embodiment of the present invention.

FIG. 18 is a block diagram schematically illustrating a decodingapparatus according to an exemplary embodiment of the present invention.

MODE FOR INVENTION

The present invention may be changed and modified variously and beillustrated with reference to different exemplary embodiments, some ofwhich will be described in detail and shown in the drawings. However,these embodiments are not intended for limiting the invention. Theterminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting the technical ideaof the invention. As used herein, the singular forms “a,” “an” and “the”are intended to include the plural forms as well, unless the contextclearly indicates otherwise. It will be further understood that theterms “include” and/or “have,” when used in this specification, specifythe presence of stated features, integers, steps, operations, elements,components, and/or combinations thereof, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or combinations thereof.

Although elements illustrated in the drawings are independently shownfor convenience of description of different distinctive functions in avideo encoding apparatus/decoding apparatus, such a configuration doesnot indicate that each element is constructed by a separate hardwareconstituent or software constituent. That is, at least two elements maybe combined into a single element, or a single element may be dividedinto a plurality of elements to perform functions. It is to be notedthat embodiments in which some elements are integrated into one combinedelement and/or an element is divided into multiple separate elements areincluded in the scope of the present invention without departing fromthe essence of the present invention.

Hereinafter, exemplary embodiments of the invention will be described indetail with reference to the accompanying drawings. Like referencenumerals in the drawings refer to like elements throughout, andredundant descriptions of like elements will be omitted herein.

FIG. 1 is a block diagram schematically illustrating a video encodingapparatus according to an exemplary embodiment of the present invention.Referring to FIG. 1, the video encoding apparatus 100 includes a picturepartition module 105, a prediction module 110, a transform module 115, aquantization module 120, a rearrangement module 125, an entropy encodingmodule 130, a dequantization module 135, an inverse transform module140, a filter module 145 and a memory 150.

The picture partition module 105 may partition an input picture into atleast one block as a processing unit. Here, the block as the processingunit may be a prediction unit (PU), a transform unit (TU) or a codingunit (CU).

Processing unit blocks partitioned by the picture partition module 105may have a quadtree structure.

The prediction module 110 may include an inter prediction module toperform inter prediction and an intra prediction module to perform intraprediction, which will be described. The prediction module 110 performsprediction on the processing unit of the picture from the partitionmodule 105 to generate a prediction block. The processing unit of thepicture in the prediction module 110 may be a CU, a TU or a PU.Furthermore, the prediction module 110 may determine whether to performinter prediction or intra prediction for the processing unit, anddetermine details (for example, a prediction mode) of each predictionmethod. Here, a processing unit for performing prediction may bedifferent from a processing unit for determining a prediction method anddetails on the prediction method. For example, a prediction method and aprediction mode may be determined by each PU, while prediction may beperformed by each TU.

In inter prediction, a prediction block may be generated by performingprediction based on information on at least one of previous and/orsubsequent pictures of a current picture. In intra prediction, aprediction block may be generated by performing prediction based oninformation on a pixel within the current picture.

A skip mode, a merge mode and motion vector prediction (MVP) may be usedas an inter prediction method. In inter prediction, a reference picturemay be selected for a PU, and a reference block corresponding to the PUmay be selected. The reference block may be selected as a unit ofinteger pixel. Subsequently, a prediction block that has a minimumresidual signal with respect to the current PU and has a minimum-sizemotion vector is generated.

The prediction block may be generated as an integer sample unit or as apixel unit smaller than an integer pixel, such as a ½ pixel unit and a ¼pixel unit. Here, the motion vector may be also represented in a unitsmaller than an integer pixel.

Information including an index of the reference pixel selected in interprediction, the motion vector (e.g., a motion vector predictor) and theresidual signal is entropy-encoded and transferred to a decodingapparatus. In the skip mode, since the prediction block may be areconstructed block without a residual, the residual may not begenerated, transformed, quantized and transferred.

In intra prediction, a prediction mode may be determined by a PU, andprediction may be performed by a PU. Alternatively, a prediction modemay be determined by a PU, and intra prediction may be performed by aTU.

Intra prediction may include 33 directional prediction modes and two ormore non-directional modes. The non-directional modes may include a DCprediction mode and a planar mode.

In intra prediction, a prediction block may be generated after applyinga filter to a reference sample. Here, it may be determined based on anintra prediction mode and/or size of a current block whether to applythe filter to the reference sample.

A PU may be a block of different sizes/forms. For example, in interprediction, a PU may be a 2N×2N, 2N×N, N×2N or N×N block (N is aninteger). In intra prediction, a PU may be a 2N×2N or N×N block (N is aninteger). Here, a PU having an N×N size may be set to be applied only toa special case. For example, an N×N PU may be available only for a CUwith a minimum size or only for intra prediction. In addition to the PUswith the foregoing sizes, a PU may include N×mN, mN×N, 2N×mN and mN×2Nblocks (m<1).

A residual value (residual block or residual signal) between thegenerated prediction block and an original block is input to thetransform module 115. Also, information on a prediction mode and amotion vector used for prediction are encoded along with the residualvalue by the entropy encoding module 130 and transmitted to the decodingapparatus.

The transform module 115 transforms the residual block by a transformblock and generates a transform coefficient.

A transform block is a rectangular block of samples to which the sametransformation is applied. The transform block may be a TU and have aquadtree structure.

The transform module 115 may perform transformation based on aprediction mode applied to the residual block and a size of the block.

For example, when intra prediction is applied to the residual block andthe block has a 4×4 residual array, the transform module 115 maytransform the residual block using discrete sine transform (DST). Inother cases, the transform module 115 may transform the residual blockusing discrete cosine transform (DCT).

The transform module 115 may generate a transform block of transformcoefficients by transformation.

The quantization module 120 may quantize residual values transformed bythe transform module 115, that is, the transform coefficients, togenerate quantized transform coefficients. The coefficients generated bythe quantization module 120 are provided to the dequantization module135 and the rearrangement module 125.

The rearrangement module 125 rearranges the quantized transformcoefficients provided from the quantization module 120. Rearranging thequantized transform coefficients may enhance encoding efficiency in theentropy encoding module 130.

The rearrangement module 125 may rearrange a two-dimensional (2D) blockof the quantized transform coefficients into a one-dimensional (1D)vector using coefficient scanning.

The entropy encoding module 130 may entropy-encode the quantizedtransform coefficients rearranged by the rearrangement module 125.Various encoding methods, such as exponential Golomb, context-adaptivevariable length coding (CAVLC) and context-adaptive binary arithmeticcoding (CABAC), may be used for entropy encoding. The entropy encodingmodule 130 may encode various types of information, such as quantizedtransform coefficient information and block type information on a CU,prediction mode information, partition unit information, ICUinformation, transfer unit information, motion vector information,reference picture information, block interpolation information andfiltering information, received from the rearrangement module 125 andthe prediction module 110.

Further, the entropy coding module 130 may apply a change to a receivedparameter set or syntax as necessary.

The dequantization module 135 dequantizes the values quantized by thequantization module 120, that is, the quantized transform coefficients,and the inverse transform module 140 inverse-transforms the valuesdequantized by the dequantization module 135.

The residual values generated through the dequantization module 135 andthe inverse transform module 140 are added to the prediction blockpredicted by the prediction module 110, thereby generating areconstructed block.

FIG. 1 illustrates that a reconstructed block is generated by adding aresidual block to a prediction block through an adder. Here, the addermay be regarded as a separate module for generating a reconstructedblock (reconstructed block generation module).

The filter module 145 may apply a deblocking filter, an adaptive loopfilter (ALF), and a sample adaptive offset (SAO) to a reconstructedpicture.

The deblocking filter may remove block distortion generated onboundaries between blocks in the reconstructed picture. The ALF mayperform filtering based on a value resulting from comparing thereconstructed picture obtained by filtering blocks using the deblockingfilter with the original picture. The ALF may be employed only for highefficiency. The SAO reconstructs an offset difference between theresidual block to which the deblocking filter has been applied and theoriginal picture by a pixel unit, in which a band offset or an edgeoffset is used.

Meanwhile, the filter module 145 may not apply filtering to areconstructed block used in inter prediction.

The memory 150 may store the reconstructed block or picture obtained viathe filter module 145. The reconstructed block or picture stored in thememory 150 may be provided to the prediction module 110 performing interprediction.

FIG. 2 is a block diagram schematically illustrating a video decodingapparatus according to an exemplary embodiment of the present invention.Referring to FIG. 2, the video decoding apparatus 200 may include anentropy decoding module 210, a rearrangement module 215, adequantization module 220, an inverse transform module 225, a predictionmodule 230, a filter module 235, and a memory 240.

When a video bitstream is input from the video encoding apparatus, theinput bitstream may be decoded according to a procedure by which thevideo encoding apparatus processes video information.

For example, when the video encoding apparatus uses variable-lengthcoding (VLC), such as CAVLC, to perform entropy encoding, the entropydecoding module 210 may perform entropy decoding using the same VLCtable as used in the encoding apparatus. Also, if the video encodingapparatus uses CABAC to perform entropy ending, the entropy decodingmodule 210 may also perform entropy decoding using CABAC.

Among pieces of information decoded by the entropy decoding module 210,information for generating a prediction block may be provided to theprediction module 230, and a residual value entropy-decoded by theentropy decoding module 210, that is, a quantized transform coefficient,may be input to the rearrangement module 215.

The rearrangement module 215 may rearrange information on the bitstreamentropy-decoded by the entropy decoding module 210, that is, thequantized transform coefficients, based on a rearrangement method usedin the encoding apparatus.

The rearrangement module 215 may reconstruct and rearrange a 1D vectorof coefficients into a 2D block of coefficients. The rearrangementmodule 215 may scan coefficients based on a prediction mode of a currentblock (transform block) and a size of the transform block to generate a2D block of coefficients (quantized transform coefficients).

The dequantization module 220 may perform dequantization based on aquantization parameter provided from the encoding apparatus and therearranged coefficients of the block.

The inverse transform module 225 may perform inverse DCT and/or inverseDST on a result of quantization performed by the video encodingapparatus in response to DCT and DST performed by the transform moduleof the encoding apparatus. Inverse transformation may be performed onthe basis of a transfer unit or a picture partition unit determined bythe encoding apparatus. The transform module of the encoding apparatusmay selectively perform DCT and/or DST depending on a plurality ofinformation elements, such as a prediction method, a size of a currentblock and a prediction direction, and the inverse transform module 225of the decoding apparatus may perform inverse transformation on thebasis of information on transformation performed by the transform moduleof the encoding apparatus.

The prediction module 230 may generate a prediction block based oninformation relating to generation of the prediction block provided fromthe entropy decoding module 210 and information on a previously decodedblock and/or picture provided from the memory 240.

If a prediction mode for a current PU is an intra prediction mode, intraprediction may be performed based on information on a pixel in a currentpicture to generate the prediction block.

If the prediction mode for the current PU is an inter prediction mode,inter prediction for the current PU may be performed based oninformation on at least one of previous and subsequent pictures of thecurrent picture. Here, motion information necessary for the interprediction for the current PU provided by the video encoding apparatus,for example, information on a motion vector and a reference pictureindex, may be derived by checking a skip flag and a merge flag receivedfrom the encoding apparatus.

A reconstructed block may be generated using the prediction blockgenerated by the prediction module 230 and a residual block provided bythe inverse transform module 225. FIG. 2 illustrates that the addermerges the prediction block and the residual block to generate thereconstructed block. Here, the adder may be regarded as a separatemodule for generating the reconstructed block (reconstructed blockgeneration module).

When the skip mode is used, the prediction block may be thereconstructed block without transmitting the residual block.

The reconstructed block and/or picture may be provided to the filtermodule 235. The filter module 235 may apply deblocking filtering, SAOand/or AFL to the reconstructed block and/or picture.

The memory 240 may store the reconstructed picture or block to be usedas a reference picture or a reference block and supply the reconstructedpicture to an output unit.

Meanwhile, the encoding apparatus and the decoding apparatus maypartition a picture into predetermined units to process (encode/decode)the units.

For example, a picture may be partitioned into slices and tiles.

A slice is a sequence of one or more slice segments. A slice sequenceincludes one independent slice segment and subsequent dependent slicesegments that follows the independent slice segment before a nextindependent slice segment.

A slice segment may be a sequence of coding tree units (CTUs) or codingtree blocks (CTBs). A CTU is CUs of a quadtree, which may be a largestcoding unit (LCU). In this specification, a CTU and LCU may be replacedwith each other as necessary for better understanding.

FIG. 3 schematically illustrates a slice according to an exemplaryembodiment.

A current picture 300 is divided into two slices by a slice boundary350. A first slice may include an independent slice segment 310including four CTUs, a first dependent slice segment 320 including 32CTUs and a second dependent slice segment 340 including 24 CTUs, thefirst dependent slice segment 320 and the second dependent slice segmentbeing divided by a slice segment boundary 330.

Another independent slice segment 360 includes 28 CTUs.

A tile may be also a sequence of CTUs, CTBs or LCUs. A CTU is CUs of aquadtree, which may be an LCU. As described above, in thisspecification, a CTU and LCU may be replaced with each other asnecessary for better understanding.

In detail, a tile may be an integer number of CTUs or LCUs co-occurringwithin a region specified by one row or one column.

With respect to each slice and each tile, all or at least one of thefollowing two conditions are satisfied: (1) all CTUs or LCUs in a slicebelong to the same tile; and (2) all CTUs or LCUs in a tile belong tothe same slice.

Thus, slices including a plurality of tiles and a tile including aplurality of slices may be present within the same picture.

Further, with respect to each slice segment and each tile, all or atleast one of the following two conditions are satisfied: (1) all CTUs orLCUs in a slice segment belong to the same tile; and (2) all CTUs orLCUs in a tile belong to the same slice segment.

FIG. 4 schematically illustrates a tile and a slice according to anexemplary embodiment.

A current picture 400 includes only a single slice and is divided intotwo right and left tiles based on a tile boundary 410. The slice in thecurrent picture 400 includes an independent slice segment 420 and fourdependent slice segments divided by slice segment boundaries 430, 440and 450.

FIG. 5 schematically illustrates a tile and a slice according to anotherexemplary embodiment.

A current picture 500 is divided into two right and left tiles based ona tile boundary 510. The left tile on the tile boundary 510 includes twoslices based on a slice boundary 550. An upper slice on the sliceboundary 550 includes an independent slice segment 520 and a dependentslice segment 540, while a lower slice on the slice boundary 550includes an independent slice segment 530 and a dependent slice segment560. A next slice based on a slice boundary 590, that is, a slice in asecond tile, includes an independent slice segment 570 and a dependentslice segment 580.

Encoding and decoding may be performed by a tile, a row of CTUs(hereinafter, a row or stream of CTUs or a row or stream of LCTs isreferred to as a “substream” for convenience of description). Eachsample in a tile or substream may be processed by a CTU or LCU.

Here, decoding may be performed in parallel. For example, decoding maybe performed in parallel by tiles. Alternatively, decoding may beperformed in parallel by substreams.

For instance, when entropy decoding is carried out by substreams, whenentropy-decoding of an n^(th) substream (n is an integer) starts, aftera second CTU or LCU of the n^(th) substream is entropy-decoded, then ann+1^(th) substream may be entropy-decoded.

A substream may be part of a bitstream to be decoded in each decodingprocess when a plurality of decoding processes are performed inparallel, which may be a row of LCUs or CTUs.

Here, when the second CTU or LCU of the n^(th) substream (an n^(th) rowof CTUs or LCUs) is completely entropy-decoded, related contextinformation is stored. A first CTU or LCU of the n+1^(th) substream maybe entropy-decoded based on the context information on the second CTU orLCU of the n^(th) substream.

As such, parsing substreams in parallel at an interval of one CTU or LCUis defined as wavefront parallel processing (WPP).

Unlike in WPP, tiles may be simultaneously decoded in a tile structure.Here, a maximum number of tiles to be processed in parallel may bepredetermined. For example, at most four tiles may be set to beprocessed in parallel. When the number of tiles to be processed inparallel is four or fewer, the decoding apparatus may process one tofour tiles at once.

The tile structure and WPP enable the encoding apparatus to partition apicture into a plurality of sections. The decoding apparatus may decodethe partitioned sections in a parallel manner.

An access point of a bitstream for performing parallel decoding usingthe tile structure (tile substream) or WPP substream is defined as anentry point. For example, an entry point may be a start point of eachWPP substream or each tile of a bitstream to be subjected to parallelprocessing.

Thus, to allow parallel processing, it is important to signal an entrypoint of each tile or entry point of a slice header of a WPP substream.Although a tile and WPP may employ different encoding/decodingtechniques, an entry point of a tile and an entry point of a substreamapplied WPP may be signaled in the same manner.

In parallel processing, a tile always starts at a byte aligned location,whereas a substream applied WPP (“WPP substream”) may not start at abyte aligned location. Byte alignment means alignment in bytes.

Since a tile and a WPP substream are different in bit granularity withrespect to an entry point, it may be important to know whether a lengthof a partition, that is, a WPP substream of a tile, is signaled based ona byte, bits or bytes.

FIG. 6 schematically illustrates a WPP substream.

In FIG. 6, a predetermined region 600 of a picture includes a pluralityof substreams, such as substream A 610, substream B 620 and substream C630.

Each substream is sequentially decoded from a first LCU. Second andsubsequent LCUs of each substream may be entropy-decoded based onresults of entropy decoding previous LCUs, that is, context.

In WPP, substreams may be decoded in parallel, in which first LCUs ofsubstreams subsequent to a first substream may be entropy-decoded basedon values of context variables with respect to second LCUs of previoussubstreams.

For example, in parallel decoding using WPP, decoding is carried outfrom a first LCU A1 of a first row 610 in a decoding target region 600.When a second LCU A2 of the first row 610 is completely entropy-decoded,the decoding apparatus stores values of context variables with respectto A2.

A first LCU B1 of a second row 620 is entropy-decoded based on thevalues of the context variables with respect to the second LCU A2 of thefirst row 610. When a second LCU B2 of the second row 620 is completelyentropy-decoded, the decoding apparatus stores values of contextvariables with respect to B2.

A first LCU C1 of a third row 630 is entropy-decoded based on the valuesof the context variables with respect to the second LCU B2 of the secondrow 620. When a second LCU C2 of the third row 630 is completelyentropy-decoded, the decoding apparatus stores values of contextvariables with respect to C2.

Likewise, fourth and subsequent rows may be subjected to entropydecoding using values of context variables with respect to second LCUsof previous rows.

When WPP is employed, an entry point may indicate a decoding start point(access point) of each substream.

In FIG. 6, the predetermined region 600 of the picture may be part ofthe current picture, a slice of the current picture or an entire regionof the current picture.

FIG. 7 schematically illustrates a tile.

In FIG. 7, a predetermined region 700 of a picture is divided into tile1 710, tile 2 720, tile 3 730 and tile 4 740. Each tile includes aplurality of substreams.

When the tile structure is employed, the decoding apparatus may decodethe tiles in parallel. As illustrated above, when a maximum number oftiles to be decoded in parallel is 4, the decoding apparatus may decodetiles 1 to 4 at the same time.

In decoding the tiles in parallel, substreams are decoded in order froma first substream of each tile, for example, A→B→C→ etc., in which ICUsin a substream are decoded in order from a first LCU, for example,Xx1→Xx2→Xx3→, etc.

When the tile structure is applied, entry points may indicate decodingstart points access points) of the respective tiles.

In FIG. 7, the predetermined region 700 of the picture may be part ofthe current picture, a slice of the current picture or an entire regionof the current picture.

Meanwhile, both WPP and tiles may be applied.

FIG. 8 schematically illustrates a relationship between WPP and tiles.

When both WPP and tiles are employed, a WPP substream is applied in atile as illustrated in FIG. 8.

In FIG. 8, a predetermined region 800 of a picture is divided into tile1 810, tile 2 820, tile 3 830 and tile 4 840. Each tile includes aplurality of substreams.

As shown in FIG. 8, substreams A and B are alternately disposed in tile1 810, substreams C and D are alternately disposed in tile 2 820,substreams E and F are alternatively disposed in tile 3 830, substreamsG and H are alternatively disposed in tile 4 840.

Thus, considering application of tiles and WPP, content indicated bysignaled entry points may need to be specified separately when neither atile nor WPP is used, when a tile is used, when WPP is used and whenboth a tile and WPP are used. For example, types of entry points may bespecified as follows.

(i) If neither a tile nor WPP is used, no entry point is present.

(ii) If a tile is used and WPP is not used, all entry points are entrypoints of the tile.

(iii) If a tile is not used and WPP is used, all entry points are entrypoints of a WPP substream.

(iv) If both a tile and WPP are used, an i-th entry point is an entrypoint of both a tile and a WPP substream when an i % number of WPPsubstreams is 0 while the i-th entry point is an entry point of a WPPsubstream when the i % number of WPP substreams is not 0.

In FIG. 8, the predetermined region 800 of the picture may be part ofthe current picture, a slice of the current picture or an entire regionof the current picture.

As described above, in parallel decoding, a start point (access point)of each parallel processing in indicated by an entry point. Thus,various methods of signaling an entry point for the encoding apparatusand various methods of receiving a signaled entry point and performingparallel decoding for the decoding apparatus may be considered.

Hereinafter, signaling of entry point information will be described indetail with reference to exemplary embodiments.

Embodiment 1

Table 1 illustrates a syntax element in a slice header used to signalentry points of a WPP substream and a tile.

TABLE 1 Descriptor slice_header( ) {   ...  entry_point_locations_flagu(1)  if entry_point_locations_flag == 1) {   entry_point_locations ( ) } }

In Table 1, entry point information may be information on an entry pointof a WPP substream or information on an entry point of a tile.

entry_point_location_flag specifies whether entry point information ispresent in a bitstream. For example, if the entry point information, forinstance, entry point location information, is present in the bitstream,entry_point_location_flag is 1. If the entry point information is absentin the bitstream, entry_point_location_flag is 0.

Table 2 illustrates a syntax structure relating to the entry pointlocation information in Table 1.

TABLE 2 Descriptor entry_point_locations( ) { num_of_entry_points_minus1 ue(v)  entry_point_offset_length_minus2ue(v)  for (i=0; i<num_of_entry_points_minus1; i++) {  entry_point_offset[i] u(v)  } }

In Table 2, the entry point information may be information on an entrypoint of a WPP substream or information on an entry point of a tile.

num_of_entry_points_minus1 specifies a number of entry points in thebitstream in a slice. Since a number of entry point offsets is smallerby 1 than the number of entry points, num_of_entry_points_minus1 mayalso specify a number of syntax elements entry_point_offset[i] in theslice header.

entry_point_offset_length_minus2 specifies a number of bits used tosignal information on an entry point offset (syntax elemententry_point_offset). That is, entry_point_offset_length_minus2 mayspecify a length of syntax element entry_point_offset[i] in bits orbytes.

entry_point_offset[i] specifies a number of bits between two entrypoints. Here, when i is 0, entry_point_offset[0] specifies a number ofbits between an end of the slice header and a first entry point in aslice. When i is not 0, entry_point_offset[i] specifies a number of bitsbetween an entry point i−1 and an entry point i.

If the length of entry_point_offset[i] is xx, xx may be defined asEquation 1.xx=(num_substreams_minus1>0)?entry_point_offset_length_minus2+5:entry_point_offset_length_minus2+2  [Equation1]

In Equation 1, WPP may be employed when a number of substreams isgreater than 1, while a tile may be used when the number of substreamsis 1 or smaller.

In this case, an entry point type, that is, whether an entry point isabout a tile or about a WPP substream, may be inferred as follows.

(1) If tile_info_present_flag is 1 and num_substream_minus1 is 0, thatis, tile_info_present_flag==1 && num_substream_minus1==0, all entrypoints are entry points of tiles. That is, if tile information ispresent and the number of substreams is 1, all entry points may beinferred as entry points of tiles.

(2) If tile_info_present_flag is 0 and num_substream_minus1 is greaterthan 0, that is, tile_info_present_flag==0 && num_substream_minus1>0,all entry points are entry points of WPP substreams. That is, if tileinformation is absent and a plurality of substreams is present, allentry points may be inferred as entry points of WPP substreams.

(3) If tile_info_present_flag is 1 and num_substream_minus1 is greaterthan 0, that is, tile_info_present_flag==1 && num_substream_minus1>0,when i is not 0 (i!=0) and (i+1)%(num_substream1+1)==0, an i-th entrypoint is an entry point of a tile that is an i-th entry point.Otherwise, entry points are entry points of WPP substreams, That is, iftile information is present and a plurality of substreams is present,entry points may be inferred as entry points of WPP substreams or entrypoints of tiles and WPP substreams.

Embodiment 2

When WPP is employed, a stream (for example, a bitstream) of encodeddata in a slice may be partitioned into one or more substreams.

A substream may be a unit of parallel processing (parallel decoding),and each substream is aligned in bits. In this specification,“aligning/aligned in bits” is expressed as “bit-aligning/aligned” forconvenience of description.

Thus, a length of each substream may be expressed in bits, and an entrypoint thereof may be also expressed in bits.

FIG. 9 schematically illustrates order of LCUs in a picture.

Referring to FIG. 9, a predetermined region 910 of a picture includestwo substreams which are substream A as a 0-th substream and substream Bas a first substream. Substream A includes LCUs Ax (x=1, 2, . . . , 7and 8) and substream B includes LCUs Bx (x=1, 2, . . . , 7 and 8).

In FIG. 9, substreams A and B are alternately disposed in the region910.

The region 910 of the picture may be part of the current picture, aslice or tile of the current picture, an entire region of the currentpicture. An LCU may be a CTU.

FIG. 10 schematically illustrates order of LCUs in a bitstream. In FIG.10, the bitstream is formed of the LCUs illustrated in FIG. 9.

Referring to FIG. 10, the bitstream 1010 includes two substreams whichare substream A as a 0-th substream and substream B as a firstsubstream. Substream A includes LCUs Ax (x=1, 2, . . . , 7 and 8) andsubstream B includes LCUs Bx (x=1, 2, . . . , 7 and 8).

In the bitstream 1010, an entry point 1020 of substream A may correspondto a start point of LCU A1, and an entry point 1030 of substream B maycorrespond to a start point of LCU B1.

In FIG. 9, when the region 910 is a tile and a tile structure isemployed instead of WPP, the entry point 1030 may be an entry point ofthe tile.

As described above, the substreams of FIG. 10 have a length in bits, andthe entry points are expressed in bits.

In this connection, aligning a substream in bytes, not in bits, may beconsidered. In this specification, “aligning/aligned in bytes” isexpressed as “byte-aligning/aligned” for convenience of description.

Thus, WPP substreams are byte-aligned when WPP is employed, whilesubstreams in a tile may be byte-aligned when the tile structure isemployed.

Byte-aligned bits may be used to byte-align substreams. A byte-alignedbit is a bit to be added to a bitstream or substream so as to byte-aligneach substream.

For instance, when each stream (WPP substream or substream of a tile) isnot byte-aligned at an end thereof, a byte-aligned bit may be added.Thus, a length of each substream is expressed in bytes, not in bits.

A byte-aligned bit may be added to a predetermined section of asubstream to be subjected to byte alignment. For example, a byte-alignedbit may be added to an end of each substream.

FIG. 11 schematically illustrates byte alignment of a substream.

In FIG. 11, the bitstream is formed of the LCUs illustrated in FIG. 9.

Referring to FIG. 11, the bitstream 1110 includes two substreams whichare substream A as a 0-th substream and substream B as a firstsubstream. Substream A includes LCUs Ax (x=1, 2, . . . , 7 and 8) andsubstream. B includes LCUs Bx (x=1, 2, . . . , 7 and 8).

In the bitstream 1110, an entry point 1120 of substream A may correspondto a start point of LCU A1, and an entry point 1130 of substream B maycorrespond to a start point of LCU B1.

In FIG. 9, when the region 910 is a tile and the tile structure isemployed instead of WPP, the entry point 1130 may be an entry point ofthe tile.

When a length of substream A is not in bytes, a byte-aligned bit 1140may be added at an end of substream A, thereby expressing substream A inbytes.

When a length of substream B is not in bytes, a byte-aligned bit 1150may be added at an end of substream B, thereby expressing substream B inbytes.

When a substream is byte-aligned and both a tile and a WPP substream arepossibly expressed in a byte level, an entry point may be signaled in asimpler manner with granularities of entry points of the tile and WPPsubstream being the same.

Table 3 illustrates a syntax element in a slice header used to signalentry points of a WPP substream and a tile.

TABLE 3 Descriptor slice_header( ) {   ...  entry_point_locations_flagu(1)  if (entry_point_locations_flag == 1) {    entry_point_locations ()  } }

In Table 3, entry point information may be information on an entry pointof a WPP substream or information on an entry point of a tile.

entry_point_location_flag specifies whether entry point information ispresent in a bitstream. For example, if the entry point information, forinstance, entry point location information, is present in the bitstream,entry_point_location_flag is 1. If the entry point information is absentin the bitstream, entry_point_location_flag is 0.

Table 4 illustrates a syntax structure relating to the entry pointlocation information in Table 3.

TABLE 4 Descriptor entry_point_locations( ) { num_of_entry_points_minus1 ue(v)  entry_point_offset_length_minus2ue(v)  for (i=0; i<=num_of_entry_points_minus1; i++) {  entry_point_offset[i] u(v)  } }

In Table 4, the entry point information may be information on an entrypoint of a WPP substream or information on an entry point of a tile.

num_of_entry_points_minus1 specifies a number of entry points in thebitstream in a slice. Since a number of entry point offsets is smallerby 1 than the number of entry points, num_of_entry_points_minus1 mayalso specify a number of syntax elements entry_point_offset[i] in theslice header.

entry_point_offset_length_minus2 specifies a number of bits used tosignal information on an entry point offset (syntax elemententry_point_offset). That is, entry_point_offset_length_minus2 mayspecify a length of syntax element entry_point_offset[i] in bits orbytes.

entry_point_offset[i] specifies a number of bytes between two entrypoints.

When i is 0, entry_point_offset[i] specifies a number of bytes betweenan end of the slice header and a first entry point in a slice. Here, tobyte-align the end of the slice header, some initial bits of a firsttile/WPP substream may be added to the end of the slice header. Theadded bits serve as byte-aligned bits.

When i is not 0, entry_point_offset[i] specifies a number of bytesbetween an entry point i−1 and an entry point i.

Here, a length of entry_point_offset[i] isentry_point_offset_length_minus2+2.

An entry point type, that is, whether an entry point is about a tile orabout a WPP substream, may be inferred as follows.

(1) If tile_info_present_flag is 1 and num_substream_minus1 is 0, thatis, tile_info_present_flag==1 && num_substream_minus1==0, all entrypoints are entry points of tiles. That is, if tile information ispresent and the number of substreams is 1, all entry points may beinferred as entry points of tiles.

(2) If tile_info_present_flag is 0 and num_substream_minus1 is greaterthan 0, that is, tile_info_present_flag==0 && num_substream_minus1>0,all entry points are entry points of WPP substreams. That is, if tileinformation is absent and a plurality of substreams is present, allentry points may be inferred as entry points of WPP substreams.

(3) If tile_info_present_flag is 1 and num_substream_minus1 is greaterthan 0, that is, tile_info_present_flag==1 && num_substream_minus1>0,when i is not 0 (i!=0) and (i+1)%(num_substream1+1)==0, an i-th entrypoint is an entry point of a tile that is an i-th entry point.Otherwise, entry points are entry points of WPP substreams. That is, iftile information is present and a plurality of substreams is present,entry points may be inferred as entry points of WPP substreams or entrypoints of tiles and WPP substreams.

Embodiment 3

When parallel processing is employed, only an entry point of a WPPsubstream among substreams may be signaled. For example, when only WPPis employed instead of using WPP and the tile structure in combination,an entry point of a WPP substream may be signaled.

Information on the entry point of the WPP substream may be also signaledin a slice header.

Table 5 illustrates a syntax in the slice header used to signal theinformation on the entry point of the WPP substream.

TABLE 5 Descriptor slice_header( ) {  ...  if (num_substreams_minus1 >0)  {   log2_max_substream_length_minus2 ue(v)   for (i = 0; i < num_substreams_minus1; i++)   {    substream_length [i] u(v)   }  } ... }

In Table 5, log_max_substream_length_minus2 specifies a number of bitsused to signal information on a length of the substream,substream_length[i].

substream_length[i] specifies a number of bits between two entry points.Here, the two entry points may be about the WPP substream.

When i is 0 substream_length[i] specifies a number of bits between anend of the slice header and a first entry point in a slice. When i isnot 0, substream_length[i] specifies a number of bits between an entrypoint i−1 and an entry point i.

Further, as in Embodiment 2, the length of the substream may beexpressed in bytes. In this case, substream_length[i] specifies a numberof bytes between two WPP-substream entry points.

Although the present embodiment illustrates that the information on thelength of the substream is transmitted considering that only the entrypoint of the WPP substream is transmitted, an entry point offset may bealso transmitted as in Embodiments 1 and 2, instead of the length of thesubstream.

In this case, the slice header in Table 5 transmitsentry_point_offset[i] instead of substream_length[i].entry_point_offset[i] specifies a number of bytes or bits between twoentry points, in which a byte-aligned bit for byte-aligning thesubstream may be used if the number of bytes is specified.

Embodiment 4

Unlike in the foregoing embodiments, an entry point type, that is,whether an entry point is about a tile or about a WPP substream, may bedirectly signaled, instead of being inferred.

Table 6 illustrates a syntax in a slice header used to signalinformation on an entry point.

TABLE 6 Descriptor slice_header( ) {   ...  entry_point_locations_flagu(1)  if (entry_point_locations_flag == 1) {    entry_point_locations ()  } }

In Table 6, entry_point_location_flag specifies whether entry pointinformation is present in a bitstream. For example, if the entry pointinformation, for instance, entry point location information, is presentin the bitstream, entry_point_location_flag is 1. If the entry pointinformation is absent in the bitstream, entry_point_location_flag is 0.

Table 7 illustrates a syntax relating to the entry point locationinformation in Table 6.

TABLE 7 entry_point_locations( ) Descriptor { num_of_entry_points_minus1 ue(v)  entry_point_offset_length_minus2ue(v)  for (i=0; i<num_of_entry_points_minus1; i++) {  entry_point_type[i] u(1)   entry_point_offset[i] u(v)  } }

num_of_entry_points_minus1 specifies a number of entry points in thebitstream in a slice. Since a number of entry point offsets is smallerby 1 than the number of entry points, num_of_entry_points_minus1 mayalso specify a number of syntax elements entry_point_offset[i] in theslice header.

entry_point_offset_length_minus2 specifies a number of bits used tosignal information on an entry point offset (syntax elemententry_point_offset). That is, entry_point_offset_length_minus2 mayrepresent a length of syntax element entry_point_offset[i] in bits orbytes.

entry_point_type[i] specifies an entry point type. For instance,entry_point_type[i] equal to 1 specifies an entry point of a WPPsubstream, and entry_point_type[i] equal to 0 specifies an entry pointof both a tile and a WPP substream.

entry_point_offset[i] specifies a number of bits or bytes between twoentry points. When i is 0, entry_point_offset[0] specifies a number ofbits or bytes between an end of the slice header and a first entry pointin a slice. When i is not 0, entry_point_offset[i] specifies a number ofbits or bytes between an entry point i−1 and an entry point i.

When entry_point_offset[i] specifies a number of bytes between two entrypoints, a byte-aligned bit for byte-alignment may be used.

If the length of entry_point_offset[i] is xx, xx may be defined asEquation 2.xx=(num_substreams_minus1>0)?entry_point_offset_length_minus2+5:entry_point_offset_length_minus2+2  [Equation2]

In Equation 2, WPP may be employed when a number of substreams isgreater than 1, while a tile may be used when the number of substreamsis 1 or smaller.

Embodiment 5

Information on a length of an entry point offset may be signaled in adifferent manner from in Embodiment 1.

Table 8 illustrates a syntax element in a slice header used to signalentry points of a WPP substream and a tile.

TABLE 8 slice header( ) { Descriptor  . . .  entry_point_locations_flagu(1)  if (entry_point_locations_flag == 1) {   entry_point_locations ( ) } }

In Table 8, entry point information may be information on an entry pointof a WPP substream or information on an entry point of a tile.

entry_point_location_flag specifies whether entry point information ispresent in a bitstream. For example, if the entry point information, forinstance, entry point location information, is present in the bitstream,entry_point_location_flag is 1. If the entry point information is absentin the bitstream, entry_point_location_flag is 0.

Table 9 illustrates a syntax structure relating to the entry pointlocation information in Table 8.

TABLE 9 entry_point_locations( ) Descriptor { num_of_entry_points_minus1 ue(v)  entry_point_offset_length_minus1ue(v)  for (i=0; i<num_of_entry_points_minus1; i++) {  entry_point_type[i] u(1)   entry_point_offset[i] u(v)  } }

In Table 9, the entry point information may be information on an entrypoint of a WPP substream or information on an entry point of a tile.

num_of_entry_points_minus1 specifies a number of entry points in thebitstream in a slice. Since a number of entry point offsets is smallerby 1 than the number of entry points, num_of_entry_points_minus1 mayalso specify a number of syntax elements entry_point_offset[i] in theslice header.

entry_point_offset_length_minus1 specifies a number of bits used tosignal information on an entry point offset (syntax elemententry_point_offset). That is, entry_point_offset_length_minus1 mayspecify a length of syntax element entry_point_offset[i] in bits orbytes.

entry_point_type[i] specifies an entry point type. For instance,entry_point_type[i] equal to 1 specifies an entry point of a WPPsubstream, and entry_point_type[i] equal to 0 specifies an entry pointof both a tile and a WPP substream.

entry_point_offset[i] specifies a number of bits or bytes between twoentry points. When i is 0, entry_point_offset[0] specifies a number ofbits or bytes between an end of the slice header and a first entry pointin a slice. When i is not 0, entry_point_offset[i] specifies a number ofbits or bytes between an entry point i−1 and an entry point i.

When an entry point is expressed in bytes, that is, a substream isbyte-aligned, a byte-aligned hit may be used as described above inEmbodiment 2.

When a number of bits used to transmit an entry point offset isspecified using entry_point_offset_length_minus1, if the length ofentry_point_offset[i] is xx, xx may be defined as Equation 3.xx=(num_substreams_minus1>0)?entry_point_offset_length_minus1+4:entry_point_offset_length_minus1+1  [Equation3]

In Equation 3, WPP may be employed when a number of substreams isgreater than 1, while a tile may be used when the number of substreamsis 1 or smaller.

Embodiment 6

entry_point_location_flag specifying whether entry point information ispresent in a bitstream may be inferred or derived, instead of beingsignaled as in the foregoing embodiments.

For example, presence of entry point information may be inferred asfollows, without transmitting a syntax element in a slice header whichindicates whether entry point information is present in a bitstream.

In detail, when a number of rows in a tile is greater than 1 or a numberof columns in the tile is greater than 1 and a number of substreams isgreater than 1, it is inferred that entry point information is presentin a bitstream. Otherwise, it is inferred that entry point informationis absent in a bitstream.

Table 10 illustrates a method of inferring presence of entry pointinformation.

TABLE 10 If ( ( num_tile_columns_minus1 > 0 ∥ num_tile_rows_minus1 > 0 )&& num_substreams_minus1 > 0) {  entry_point_location_flag = 1 } else { entry_point_location_flag = 0 }

In Table 10, num_tile_columns_minus1+1 specifies a number of tilecolumns partitioning a picture, and num_tile_columns_minus1 may besignaled from the encoding apparatus. Also, num_tile_row_minus1+1specifies a number of tile columns partitioning a picture, andnum_tile_rows_minus1 may be signaled from the encoding apparatus.

Thus, when a slice includes a plurality of tiles and a plurality ofsubstreams, it may be inferred that entry point information is presentin a bitstream.

Table 11 illustrates a syntax in a slice header used to transmit entrypoint information.

TABLE 11 slice_header( ) { Descriptor . . . if(num_tile_columns_minus1 > 0 ∥ num_tile_rows_minus1  > 0) &&num_sub_streams_minus1 > 0) {   entry_point_locations ( )  } }

In the foregoing embodiments, entry_point_location_flag specifyingpresence of entry point information is transmitted through the sliceheader, in which entry_point_location_flag equal to 1 specifies thatentry point information is present in the bitstream.

In Table 11, when a number of rows in a tile is greater than 1 or anumber of columns in the tile is greater than 1 and a number ofsubstreams is greater than 1, it is considered that entry pointinformation is present in a bitstream. In this case, the entry pointinformation may be transmitted as in Table 10.

Table 12 illustrates a syntax transmitted when entry point informationis present in a bitstream as in Table 11.

TABLE 12 entry_point_locations( ) Descriptor { num_of_entry_points_minus1 ue(v)  entry_point_offset_length_minus1ue(v)  for (i=0; i<num_of_entry_points_minus1; i++) {  entry_point_type[i] u(1)   entry_point_offset[i] u(v)  } }

In Table 12, num_of_entry_points_minus1 specifies a number of entrypoints in the bitstream in a slice. Since a number of entry pointoffsets is smaller by 1 than the number of entry points,num_of_entry_points_minus1 may also specify a number of syntax elementsentry_point_offset[i] in the slice header.

entry_point_offset_length_minus1 specifies a number of bits used tosignal information on an entry point offset (syntax elemententry_point_offset). That is, entry_point_offset_length_minus1 mayrepresent a length of syntax element entry_point_offset[i] in bits orbytes.

entry_point_type[i] specifies an entry point type. For instance,entry_point_type[i] equal to 1 specifies an entry point of a WPPsubstream, and entry_point_type[i] equal to 0 specifies an entry pointof both a tile and a WPP substream.

entry_point_offset[i] specifies a number of bits or bytes between twoentry points. When i is 0, entry_point_offset[0] specifies a number ofbits or bytes between an end of the slice header and a first entry pointin a slice. When i is not 0, entry_point_offset[i] specifies a number ofbits or bytes between an entry point i−1 and an entry point i.

When an entry point is expressed in bytes, that is, a substream isbyte-aligned, a byte-aligned bit may be used as described above inEmbodiment 2.

Embodiment 7

When length information on an entry point offset is transmitted as inEmbodiment 4, an entry point type may be conditionally signaled.

For example, when a slice includes a plurality of tiles and a pluralityof substreams, an entry point type, that is, whether an entry type isabout a tile or about a substream, may be signaled.

Table 13 illustrates a syntax in a slice header used to signal entrypoint information.

TABLE 13 slice_header( ) { Descriptor  . . .  entry_point_locations_flagu(1)  if (entry_point_locations_flag == 1) {   entry_point_locations ( ) } }

In Table 13, entry_point_location_flag specifies whether entry pointinformation is present in a bitstream. For example, if the entry pointinformation, for instance, entry point location information, is presentin the bitstream, entry_point_location_flag is 1. If the entry pointinformation is absent in the bitstream, entry_point_location_flag is 0.

Table 14 illustrates a syntax relating to the entry point locationinformation in Table 13.

TABLE 14 entry_point_locations( ) Descriptor  num_of_entry_points_minus1ue(v)  entry_point_offset_length_minus2 ue(v)   for (i=0;i<=num_of_entry_points_minus1; i++) {      if((num_tile_columns_minus1 > 0 ∥    num_tile_rows_minus1 > 0) &&   num_substreams_minus1 > 0) {     entry_point_type[i] u(1)   }   elseif (num_substreams_minus1 > 0) {     entry_point_type [i] = 1   }   else{     entry_point_type [i] = 0   }   entry_point_offset[i] u(v)  } }

num_of_entry_points_minus1 specifies a number of entry points in thebitstream in a slice. Since a number of entry point offsets is smallerby 1 than the number of entry points, num_of_entry_points_minus1 mayalso specify a number of syntax elements entry_point_offset[i] in theslice header.

entry_point_offset_length_minus2 specifies a number of bits used tosignal information on an entry point offset (syntax elemententry_point_offset). That is, entry_point_offset_length_minus2 mayrepresent a length of syntax element entry_point_offset[i] in bits orbytes.

When a number of rows in a tile is greater than 1 or a number of columnsin the tile is greater than 1 and a number of substreams is greater than1, that is, a plurality of tiles and a plurality of substreams arepresent, entry_point_type[i] specifying an entry point type is signaled.

entry_point_type[i] specifies an entry point type. For instance,entry_point_type[i] equal to 1 specifies an entry point of a WPPsubstream, and entry_point_type[i] equal to 0 specifies an entry pointof both a tile and a WPP substream.

Thus, when a single tile or no tile is present but a plurality ofsubstreams is present, entry_point_type[i] specifies an entry point of aWPP substream. In other cases, entry_point_type[i] specifies an entrypoint of both a tile and a WPP substream.

entry_point_offset[i] specifies a number of bits or bytes between twoentry points. When i is 0, entry_point_offset[0] specifies a number ofbits or bytes between an end of the slice header and a first entry pointin a slice. When i is not 0, entry_point_offset[i] specifies a number ofbits or bytes between an entry point i−1 and an entry point i.

When entry_point_offset[i] specifies a number of bytes between two entrypoints, a byte-aligned bit for byte-alignment may be used.

If the length of entry_point_offset[i] is xx, xx may be defined asEquation 4.xx=(num_substreams_minus1>0)?entry_point_offset_length_minus2+5:entry_point_offset_length_minus2+2  [Equation4]

Embodiment 8

When length information on an entry point offset is transmitted as inEmbodiment 5, an entry point type may be conditionally signaled.

For example, when a slice includes a plurality of tiles and a pluralityof substreams, an entry point type, that is, whether an entry type isabout a tile or about a substream, may be signaled.

Table 15 illustrates a syntax in a slice header used to signal entrypoint information.

TABLE 15 slice_header( ) { Descriptor   . . . entry_point_locations_flag u(1)  if (entry_point_locations_flag == 1) {   entry_point_locations ( )  } }

In Table 15, entry_point_location_flag specifies whether entry pointinformation is present in a bitstream. For example, if the entry pointinformation, for instance, entry point location information, is presentin the bitstream, entry_point_location_flag is 1. If the entry pointinformation is absent in the bitstream, entry_point_location_flag is 0.

Table 16 illustrates a syntax relating to the entry point locationinformation in Table 15.

TABLE 16 entry_point_locations( ) Descriptor  num_of_entry_points_minus1ue(v)  entry_point_offset_length_minus1 ue(v)   for (i=0;i<=num_of_entry_points_minus1; i++) {       if((num_tile_columns_minus1 > 0 ∥     num_tile_rows_minus1 > 0) &&    num_substreams_minus1 > 0) {      entry_point_type[i] u(1)    }   else if (num_substreams_minus1 > 0) {      entry_point_type [i] = 1   }    else {      entry_point_type [i] = 0    }   entry_point_offsett[i] u(v)  } }

num_of_entry_points_minus1 specifies a number of entry points in thebitstream in a slice. Since a number of entry point offsets is smallerby 1 than the number of entry points, num_of_entry_points_minus1 mayalso specify a number of syntax elements entry_point_offset[i] in theslice header.

entry_point_offset_length_minus1 specifies a number of bits used tosignal information on an entry point offset (syntax elemententry_point_offset). That is, entry_point_offset_length_minus1 mayrepresent a length of syntax element entry_point_offset[i] in bits orbytes.

When a number of rows in a tile is greater than 1 or a number of columnsin the tile is greater than 1 and a number of substreams is greater than1, that is, a plurality of tiles and a plurality of substreams arepresent, entry_point_type[i] specifying an entry point type is signaled.

entry_point_type[i] specifies an entry point type. For instance,entry_point_type[i] equal to 1 specifies an entry point of a WPPsubstream, and entry_point_type[i] equal to 0 specifies an entry pointof both a tile and a WPP substream.

Thus, when a single tile or no tile is present but a plurality ofsubstreams is present, entry_point_type[i] specifies an entry point of aWPP substream. In other cases, entry_point_type[i] specifies an entrypoint of both a tile and a WPP substream.

entry_point_offset[i] specifies a number of bits or bytes between twoentry points. When i is 0, entry_point_offset[0] specifies a number ofbits or bytes between an end of the slice header and a first entry pointin a slice. When i is not 0, entry_point_offset[i] specifies a number ofbits or bytes between an entry point i−1 and an entry point i.

When entry_point_offset[i] specifies a number of bytes between two entrypoints, a byte-aligned bit for byte-alignment may be used.

If the length of entry_point_offset[i] is xx, xx may be defined asEquation 4.xx=(num_substreams_minus1>0)?entry_point_offset_length_minus2+4:entry_point_offset_length_minus2+1  [Equation5]

In Equation 5, WPP may be employed when a number of substreams isgreater than 1, while a tile may be used when the number of substreamsis 1 or smaller.

Embodiment 9

When length information on an entry point offset is transmitted as inEmbodiment 4, an entry point type may be inferred, instead of beingsignaled.

For example, an entry point type, that is, whether an entry point isabout a tile or about a WPP substream, may be inferred as follows.

(1) If tile_info_present_flag is 1 and num_substream_minus1 is 0, thatis, tile_info_present_flag==1 && num_substream_minus1==0, all entrypoints are entry points of tiles. That is, if tile information ispresent and the number of substreams is 1, all entry points may beinferred as entry points of tiles.

(2) If tile_info_present_flag is 0 and num_substream_minus1 is greaterthan 0, that is, tile_info_present_flag==0 && num_substream_minus1>0,all entry points are entry points of WPP substreams. That is, if tileinformation is absent and a plurality of substreams is present, allentry points may be inferred as entry points of WPP substreams.

(3) If tile_info_present_flag is 1 and num_substream_minus1 is greaterthan 0, that is, tile_info_present_flag==1 && num_substream_minus1>0,when i is not 0 (i!=0) and (i+1)%(num_substream1+1)==0, an i-th entrypoint is an entry point of a tile that is an i-th entry point.Otherwise, entry points are entry points of WPP substreams. That is, iftile information is present and a plurality of substreams is present,entry points may be inferred as entry points of WPP substreams or entrypoints of tiles and WPP substreams.

Table 17 illustrates a syntax in a slice header used to signal entrypoint information.

TABLE 17 slice_header( ) { Descriptor   . . . entry_point_locations_flag u(1)  if (entry_point_locations_flag == 1) {   entry_point_locations ( )  } }

In Table 17, entry_point_location_flag specifies whether entry pointinformation is present in a bitstream. For example, if the entry pointinformation, for instance, entry point location information, is presentin the bitstream, entry_point_location_flag is 1. If the entry pointinformation is absent in the bitstream, entry_point_location_flag is 0.

Table 18 illustrates a syntax relating to the entry point locationinformation in Table 17.

TABLE 18 entry_point_locations( ) Descriptor  num_of_entry_points_minus1ue(v)  entry_point_offset_length_minus2 ue(v)   for (i=0;i<=num_of_entry_points_minus1; i++) {    entry_point_offset[i] u(v)  } }

num_of_entry_points_minus1 specifies a number of entry points in thebitstream in a slice. Since a number of entry point offsets is smallerby 1 than the number of entry points, num_of_entry_points_minus1 mayalso specify a number of syntax elements entry_point_offset[i] in theslice header.

entry_point_offset_length_minus2 specifies a number of bits used tosignal information on an entry point offset (syntax elemententry_point_offset). That is, entry_point_offset_length_minus2 mayrepresent a length of syntax element entry_point_offset[i] in bits orbytes.

entry_point_offset[i] specifies a number of bits or bytes between twoentry points. When i is 0, entry_point_offset[0] specifies a number ofbits or bytes between an end of the slice header and a first entry pointin a slice. When i is not 0, entry_point_offset[i] specifies a number ofbits or bytes between an entry point i−1 and an entry point i.

When entry_point_offset[i] specifies a number of bytes between two entrypoints, a byte-aligned bit for byte-alignment may be used.

In Table 18, an entry point type is not directly signaled. Instead, inembodiment 9, an entry point type is inferred based ontile_info_present_flag and num_substream_minus1 as described above.

Embodiment 10

When length information on an entry point offset is transmitted as inEmbodiment 5, an entry point type may be inferred, instead of beingsignaled.

For example, an entry point type, that is, whether an entry point isabout a tile or about a WPP substream, may be inferred as follows.

(1) If tile_info_present_flag is 1 and num_substream_minus1 is 0, thatis, tile_info_present_flag==1 && num_substream_minus1==0, all entrypoints are entry points of tiles. That is, if tile information ispresent and the number of substreams is 1, all entry points may beinferred as entry points of tiles.

(2) If tile_info_present_flag is 0 and num_substream_minus1 is greaterthan 0, that is, tile_info_present_flag==0 && num_substream_minus1>0,all entry points are entry points of WPP substreams. That is, if tileinformation is absent and a plurality of substreams is present, allentry points may be inferred as entry points of WPP substreams.

(3) If tile_info_present_flag is 1 and num_substream_minus1 is greaterthan 0, that is, tile_info_present_flag==1 && num_substream_minus1>0,when i is not 0 (i!=0) and (i+1)%(num_substream1+1)==0, an i-th entrypoint is an entry point of a tile that is an i-th entry point.Otherwise, entry points are entry points of WPP substreams. That is, iftile information is present and a plurality of substreams is present,entry points may be inferred as entry points of WPP substreams or entrypoints of tiles and WPP substreams.

Table 19 illustrates a syntax in a slice header used to signal entrypoint information.

TABLE 19 slice_header( ) { Descriptor   . . . entry_point_locations_flag u(1)  if (entry_point_locations_flag == 1) {   entry_point_locations ( )  } }

In Table 19, entry_point_location_flag specifies whether entry pointinformation is present in a bitstream. For example, if the entry pointinformation, for instance, entry point location information, is presentin the bitstream, entry_point_location_flag is 1. If the entry pointinformation is absent in the bitstream, entry_point_location_flag is 0.

Table 20 illustrates a syntax relating to the entry point locationinformation in Table 19.

TABLE 20 entry_point_locations( ) Descriptor  num_of_entry_point_minus1ue(v)  entry_point_offset_length_minus1 ue(v)   for (i=0;i<=num_of_entry_points minus1; i++) {    entry_point_offset[i] u(v)  } }

num_of_entry_points_minus1 specifies a number of entry points in thebitstream in a slice. Since a number of entry point offsets is smallerby 1 than the number of entry points, num_of_entry_points_minus1 mayalso specify a number of syntax elements entry_point_offset[i] in theslice header.

entry_point_offset_length_minus1 specifies a number of bits used tosignal information on an entry point offset (syntax elemententry_point_offset). That is, entry_point_offset_length_minus1 mayrepresent a length of syntax element entry_point_offset[i] in bits orbytes.

entry_point_offset[i] specifies a number of bits or bytes between twoentry points. When i is 0, entry_point_offset[0] specifies a number ofbits or bytes between an end of the slice header and a first entry pointin a slice. When i is not 0, entry_point_offset[i] specifies a number ofbits or bytes between an entry point i−1 and an entry point i.

When entry_point_offset[i] specifies a number of bytes between two entrypoints, a byte-aligned bit for byte-alignment may be used.

In Table 20, an entry point type is not directly signaled. Instead, inembodiment 10, an entry point type is inferred based ontile_info_present_flag and num_substream_minus1 as described above.

Embodiment 11

Embodiment 11 illustrates a method based on the foregoing tenembodiments in combination with at least one of the followingmodifications or characteristics (1) to (4).

(1) When either a tile or WPP is used for parallel decoding, entry pointinformation is transmitted. Thus, entry_point_location_flag specifyingexistence of entry point information described in the foregoingembodiments may be unnecessary.

(2) Considering that a tile and WPP are not used, information specifyinga number of entry points may be transmitted using num_of_entry_points,instead of num_of_entry_points_minus1, so as to indicate a value of 0.That is, a value representing a total number of entry points may betransmitted, instead of a value representing the total number of entrypoints minus 1.

(3) WPP and a tile may not be used together. In this case, a tile is notused when WPP is employed, and WPP is not used when a tile is employed.

(4) An entry point offset may be derived from NALU data of byte 0. Byte0 may be a first byte of slice segment data.

When characteristic (1) is added, Embodiment 11 may directly signalnecessary entry point information without transmittingentry_point_location_flag specifying existence of entry pointinformation via a slice header, unlike the foregoing ten embodiments.

Table 21 illustrates a syntax in a slice header used to signal entrypoint information on a WPP substream or tile according to Embodiment 11.

TABLE 21 Slice_header( ) Descriptor {  . . .  num_of_entry_points ue(v) if (num_of_entry_points > 0)  {   entry_point_offset_length_minus1ue(v)   for i=0; i<num_of_entry_points; i++) {    entry_point_offsett[i]u(v)   }  }  . . . }

num_of_entry_points_minus1 specifies a number of entry points in thebitstream in a slice. Since a number of entry point offsets is smallerby 1 than the number of entry points, num_of_entry_points_minus1 mayalso specify a number of syntax elements entry_point_offset[i] in theslice header.

entry_point_offset_length_minus1 specifies a number of bits used tosignal information on an entry point offset (syntax elemententry_point_offset). That is, entry_point_offset_length_minus1 mayrepresent a length of syntax element entry_point_offset[i] in bits orbytes. Although the present embodiment illustrates thatentry_point_offset_length_minus1 is signaled,entry_point_offset_length_minus2 may be signaled instead ofentry_point_offset_length_minus1.

entry_point_offset[i] specifies a number of bits or bytes between twoentry points. When i is 0, entry_point_offset[0] specifies a number ofbytes between a start (byte 0) of NAL unit data and a first entry point(entry_point_offset[0]−1) in a slice. When i is not 0,entry_point_offset[i] specifies a number of bits or bytes between anentry point i−1 and an entry point i.

When entry_point_offset[i] specifies a number of bytes between two entrypoints, a byte-aligned bit for byte-alignment may be used.

The length of entry_point_offset[i] may beentry_point_offset_length_minus1+1 bits orentry_point_offset_length_minus2+2 bits.

FIG. 12 schematically illustrates an entry point of a WPP substream.

In FIG. 12, a predetermined region 1210 of a picture includes foursubstreams which are substream A, substream B, substream C and substreamD. Each substream may be an array of LCUs.

A start point of each substream may be indicated by an entry point. Forexample, if an entry point of substream A may be specified from a startpoint of a bitstream or an end point of a slice header, an entry pointof substream B is entry point 0 1220, an entry point of substream C isentry point 1 1230, and an entry point of substream D is entry point 21240.

In this case, entry point 0 1220 as a first entry point may be a valueof the end point of the slice header plus an entry point offset, forexample, entry_point_offset[0], representing a number of bytes or bitsbetween the end point of the slice header and the first entry point.Likewise, a number of bytes or bits between entry point 1 1220 as thefirst entry point and entry point 2 1230 as a second entry point may beindicated by an entry point offset, for example, entry_point_offset[1].

In FIG. 12, the predetermined region 1210 of the picture may be part ofthe current picture, a slice of the current picture or an entire regionof the current picture.

FIG. 13 schematically illustrates an entry point of a tile.

In FIG. 13, a predetermined region 1310 of a picture includes four tileswhich are tile 1, tile 2, tile 3 and tile 4.

A start point of each tile may be indicated by an entry point. Forexample, if an entry point of tile 1 may be specified from a start pointof a bitstream or an end point of a slice header, an entry point of tile2 is entry point 0 1320, an entry point of tile 3 is entry point 1 1330,and an entry point of tile 4 is entry point 2 1340.

In this case, entry point 0 1320 as a first entry point may be a valueof the end point of the slice header plus an entry point offset, forexample, entry_point_offset[0], representing a number of bytes or bitsbetween the end point of the slice header and the first entry point.Likewise, a number of bytes or bits between entry point 1 1320 as afirst entry point and entry point 2 1330 as a second entry point may beindicated by an entry point offset, for example, entry_point_offset[1].

In FIG. 13, the predetermined region 1310 of the picture may be part ofthe current picture, a slice of the current picture or an entire regionof the current picture.

FIG. 14 schematically illustrates an entry point when a tile and a WPPsubstream are employed together.

In FIG. 14, a predetermined region 1410 of a picture includes four tileswhich are tile 1 1410, tile 2 1420, tile 3 1430 and tile 4 1440.

Each tile includes two substreams. For example, tile 1 1410 includessubstream A and substream B. Tile 2 1420 includes substream C andsubstream D. Tile 3 1430 includes substream E and substream F. Tile 41440 includes substream G and substream H.

A start point of each tile and/or substream may be indicated by an entrypoint. For example, an entry point of tile 1 1410 may be specified froma start point of a bitstream or an end point of a slice header, and anentry point of substream A may also be specified from the start point ofthe bitstream or the end point of the slice header. An entry point ofsubstream B as a second substream in tile 1 1410 is entry point 0 1450.

An entry point of tile 2 1420 and substream C is entry point 1 1455. Anentry point of substream D in tile 2 1420 is entry point 2 1460.

An entry point of tile 3 1430 and substream E is entry point 1 1465. Anentry point of substream F in tile 3 1430 is entry point 2 1470.

An entry point of tile 4 1440 and substream G is entry point 1 1475. Anentry point of substream H in tile 4 1440 is entry point 2 1480.

In this case, entry point 0 1450 as a first entry point may be a valueof the end point of the slice header plus an entry point offset, forexample, entry_point_offset[0], representing a number of bytes or bitsbetween the end point of the slice header and the first entry point.

Entry point 1 1455 as a second entry point may be indicated by a valueof entry point 0 1450 as the first entry point plus an entry pointoffset, for example entry_point_offset[1]. Entry point 2 1460 as a thirdentry point may be indicated by a value of entry point 1 1455 as thesecond entry point plus an entry point offset, for exampleentry_point_offset[2]. Entry point 3 1465 as a fourth entry point may beindicated by a value of entry point 2 1460 as the third entry point plusan entry point offset, for example entry_point_offset[3]. Entry point 41470 as a fifth entry point may be indicated by a value of entry point 31465 as the fourth entry point plus an entry point offset, for exampleentry_point_offset[4]. Entry point 5 1475 as a sixth entry point may beindicated by a value of entry point 4 1470 as the fifth entry point plusan entry point offset, for example entry_point_offset[5]. Entry point 61480 as a seventh entry point may be indicated by a value of entry point5 1475 as the sixth entry point plus an entry point offset, for exampleentry_point_offset[6].

FIG. 15 is a flowchart schematically illustrating an encoding methodaccording to an exemplary embodiment of the present invention.

Referring to FIG. 15, an encoding apparatus Wray convert an input videosignal (S1510). The encoding apparatus may partition an input pictureinto encoding units and perform prediction based on the partitionedencoding units or subdivided units. The encoding apparatus generates aresidual as a difference between a prediction result and an originalsignal. The encoding apparatus transforms and quantizes the residual.DCT and/or DST may be used for transformation.

Prediction methods, transform methods and quantization methods areillustrated above in FIG. 1.

The encoding apparatus may entropy-encode the converted signal (S1520).CABAC, VLC and exponential Golomb may be used for entropy encoding.

The encoding apparatus signals entropy-encoded video information andinformation necessary for decoding via a bitstream (S1530). Whenparallel decoding is employed, the signaled information may includeinformation necessary for parallel processing, for example, entry pointinformation, in a slice header.

As described above, the entry point information includes entry pointoffset information, information on a number of entry points andinformation on a length of an entry point offset.

For example, entry point offset information, entry_point_offset[i],transmitted via a slice header specifies an i-th entry point offset inbytes. entry_point_offset[i] may be represented by the information onthe length of the entry point offset. For instance, if informationspecifying a length of an entry point offset isentry_point_offset_length_minus1, the entry point offset may berepresented by a value of entry_point_offset_length_minus1 plus one bit.

Slice segment data following the slice header may include a number ofsubsets specified by information on a number of entry points, andparallel decoding may be performed by a subset. Since the number ofentry points is greater by 1 than a number of entry point offsets foroffsetting neighboring entry points, the number of entry points in aslice may be specified based on the number of entry point offsetssignaled via the slice header. For example, when the number of entrypoint offsets is N, N+1 subsets are present.

As described above, an i-th entry point in the slice is a value of an(i−1)-th entry point plus an i-th entry point offset.

Alternatively, a range of an i-th subset among the subsets forming theslice segment data may be specified using the i-th entry point offset.For example, a 0-th subset may have a range from a first byte (byte 0)of the slice segment data to a 0-th entry point offset-1. A first bytein the range of the i-th subset (i is an integer excluding 0) is sum ofprevious subsets that is a sum of previous entry point offsets, and alast byte is a value of the first byte plus the i-th entry point offset,minus a 1 bit.

As described above, the information on the number of entry point offsetsmay specify a number of syntax elements entry_point_offset[i] in theslice header. For example, when WPP is employed, the number of entrypoint offsets may have a value in a range from 0 to a number of CTB rowsin the picture. When a tile is employed, the number of entry pointoffsets may have a value in a range from 0 to a number of tiles−1. Whena tile and WPP are employed together, the number of entry point offsetsmay have a value range from 0 to a number of tile columns*a number ofCTB rows−1.

Furthermore, the information on the number of entry point offset syntaxelements specifies the number of syntax elements entry_point_offset[i]in the slice header. For example, since the number of entry pointoffsets is smaller by 1 than the number of entry points, the informationon the number of entry point offset syntax elements may be transmittedas num_of_entry_point_minus1. Alternatively, the number of entry pointoffsets may be directly transmitted as num_of entry_point_offset.

The information on the length of the entry point offset may specify alength of syntax element entry_point_offset[i] in bits. For instance, ifinformation on a length of an entry point offset syntax element istransmitted as entry_point_offset_length_minus1, the length of the entrypoint offset syntax element is entry_point_offset_length_minus1+1 bits.Alternatively, if the information on the length of the entry pointoffset syntax element is transmitted asentry_point_offset_length_minus2, the length of the entry point offsetsyntax element is entry_point_offset_length_minus2+2 bits. The length ofthe entry point offset syntax element may be also transmitted as asyntax element of entry_point_offset_length, in which case the length ofthe entry point offset syntax element is entry_point_offset_length bits.

FIG. 16 is a block diagram schematically illustrating an encodingapparatus according to an exemplary embodiment of the present invention.

Referring to FIG. 16, the encoding apparatus 1600 includes a signalconversion module 1610, an entropy encoding module 1620 and a signalingmodule 1630.

The signal conversion module 1610 may partition an input picture (video)into encoding units and perform prediction based on the partitionedencoding units or subdivided units. The signal conversion module 1610generates a residual as a difference between a prediction result and anoriginal signal. The signal conversion module 1610 transforms andquantizes the residual. DCT and/or DST may be used for transformation.

The signal conversion module 1610 may include the picture partitionmodule 105, the prediction module 110, the transform module 115, thequantization module 120 and the rearrangement module 125 and performequivalent operations to those of the picture partition module 105, theprediction module 110, the transform module 115, the quantization module120 and the rearrangement module 125.

The entropy encoding module 1620 may entropy-encode the signal outputfrom the signal conversion module 1610.

The entropy encoding module 1620 may correspond to the entry encodingmodule 130 of FIG. 1 and perform equivalent operations to those of theentropy encoding module 130.

The signaling module 1630 signals encoded video information andinformation necessary for decoding via a bitstream. When paralleldecoding is employed, the signaled information may include informationnecessary for parallel processing, for example, entry point information,in a slice header.

The entry point information includes entry point offset information,information on a number of entry points and information on a length ofan entry point offset.

As described above, an i-th entry point in a slice is a value of an(i−1)-th entry point plus an i-th entry point offset. Thus, theinformation on the number of entry points may be informationrepresenting a number of entry point offset informations transmitted inthe slice header.

FIG. 17 is a flowchart schematically illustrating a decoding methodaccording to an exemplary embodiment of the present invention.

Referring to FIG. 17, a decoding apparatus receives signaling aboutvideo information from an encoding apparatus (S1710). The videoinformation may be signaled via an encoded bitstream.

The decoding apparatus may entropy-decode the received bitstream(S1720). The decoding apparatus may receive data bits transmitted in thebitstream to output syntax element values. A syntax element refers to anelement of data represented in the bitstream.

When parallel decoding is performed, data may be byte-aligned. Here,byte-aligning data means putting the data at a position in the bitstreamin bytes. For example, when the position in the bitstream is an integermultiple of 8 bits from a first bit of the bitstream, the position isbyte-aligned.

Byte alignment of a substream is described above.

When CABAC is employed for entropy decoding, the decoding maysequentially conduct initialization, binarization and decoding.

The decoding apparatus may perform initialization when at least one ofparsing slice segment data, parsing a first CTU or LCU of a tile andparsing a first CTU or LCU in a row of CTUs or LCUs starts.

The decoding apparatus may generate initial values of parameters forperforming CABAC by initialization.

Binarization is a set of bin strings with respect to values of syntaxelements. Binarization is a unique mapping process of mapping possiblevalues of syntax elements to a set of bin strings.

The decoding apparatus may output a syntax element value by mapping witha bin string, that is, a binary sequence or binary code, bybinarization. The decoding apparatus may use a table of mapping a syntaxelement to a bin string for binarization.

The decoding apparatus may determine a syntax element value through adecoding process of CABAC. The decoding apparatus may determine a binindex for each bin of a bin string and determine a context index basedon the bin index. The decoding apparatus may determine a random variablewith respect to a bin string to be decoded using the context index andoutput a syntax element value. The decoding apparatus may use a tableand also consider a type of a picture or slice (I slice, B slice or Pslice) to be decoded when determining the context index based on the binindex.

The row of the CTUs or LCUs may be a WPP substream. If WPP is employed,when a second CTU or LCU in an n-th substream (n-th row of CTU or LCUrow) is completely entropy-decoded, related context information may bestored. A first CTU or LCU in an (n+1)-th substream may be initializedbased on the context information on the second CTU or LCU in the n-thsubstream.

The decoding apparatus may reconstruct a picture based on the syntaxelement values (S1730). As described above, the syntax element valuesmay be signaled from the encoding apparatus and obtained via entropydecoding.

When parallel decoding is performed, a tile or WPP may be used. In thiscase, syntax elements may include information specifying an entry pointof a tile or information specifying an entry point of a WPP substream.

Syntax elements specifying entry points, for example, a syntax elementspecifying a number of entry points, a syntax element specifying anentry point offset, a syntax element specifying a length of a syntaxelement relating to an entry point offset, a syntax element specifyingan entry point type and a syntax element specifying existence of entrypoint information, have been described above.

Here, the syntax elements about the entry points transmitted from theencoding apparatus may be all or part of the syntax elements describedabove in the foregoing embodiments.

Although FIG. 17 illustrates the entropy decoding operation (S1720) andthe reconstructing operation (S1730) separately for betterunderstanding, the entropy decoding operation (S1720) and thereconstructing operation (S1730) may be considered as a single decodingoperation.

FIG. 18 is a block diagram schematically illustrating a decodingapparatus according to an exemplary embodiment of the present invention.

Referring to FIG. 18, the decoding apparatus 1800 includes a signalingreception module 1810, an entropy decoding module 1820 and areconstruction module 1830.

The signaling reception module 1810 receives signaling about videoinformation from an encoding apparatus. The video information may besignaled via an entropy-encoded bitstream.

The entropy decoding module 1820 may entropy-decode the receivedbitstream. The decoding apparatus may receive data bits transmitted inthe bitstream to output syntax element values. Entropy decoding has beendescribed above with reference to FIG. 17.

The entropy decoding module 1820 corresponds to the entropy decodingmodule 210 of FIG. 2.

The reconstruction module 1830 may reconstruct a picture based on thesyntax element values output from the entropy decoding module 1820. Thereconstruction module 1830 may include the rearrangement module 215, thedequantization module 220, the inverse transform module 225, theprediction module 230, the filter module 235 and the memory 240 andperform equivalent operations to those of the rearrangement module 215,the dequantization module 220, the inverse transform module 225, theprediction module 230, the filter module 235 and the memory 240.

Although FIG. 18 illustrates the entropy decoding module 1820 and thereconstruction module 1830 separately for better understanding, theentropy decoding module 1820 and the reconstruction module 1830 may beconfigured as a single decoding module.

Although methods of illustrative systems have been described with aseries of stages or blocks based on the flowcharts, the presentinvention is not limited to the foregoing sequence of the stages. Somestages may be carried out in different order from described above or atthe same time. Further, it should be noted that as the aforementionedembodiments may include various aspects of examples. Thus, it will beappreciated that changes, modifications and alternatives may be made inthese exemplary embodiments without departing from the principles andspirit of be the invention, the scope of which is defined in theappended claims and their equivalents.

It will be understood that when an element is referred to as being“coupled to” or “connected to” another element, the element can bedirectly coupled to or connected to another element or layer orintervening elements or layers. In contrast, when an element is referredto as being “directly coupled to” or “directly connected to” anotherelement or layer, there are no intervening elements or layers present.

The invention claimed is:
 1. A video encoding method, performed by anencoding apparatus, comprising: deriving entry point informationspecifying an entry point of a substream for a picture; encoding theentry point information to generate a bitsream; and outputting thegenerated bitstream, wherein the entry point information include anumber syntax element representing a number of offset syntax elements ina slice header, wherein the entry point information includes an offsetsyntax element when the number of the offset syntax elements is largerthan 0, wherein the offset syntax element represents an entry pointoffset between two entry points, wherein the entry point informationincludes a length syntax element when the number of the offset syntaxelements is larger than 0, wherein the length syntax element representsa bits length for the offset syntax element, wherein the offset syntaxelement represents the number of bytes between the two entry points,wherein a value of the length syntax element plus one corresponds to thebits length of the offset syntax element, wherein a value of the numbersyntax element corresponds to the number of offset syntax elements inthe slice header, and wherein the entry point information is configuredin the slice header.
 2. The method of claim 1, wherein the number of theoffset syntax elements is determined based on whether two or more tilesare present in the picture and whether rows of coding tree units in thepicture are parallel decoded.
 3. The method of claim 2, wherein amaximum value of the number syntax element is determined as a number ofthe rows of coding tree units in the picture minus one when two or moretiles are not present in the picture and the rows of coding tree unitsare parallel decoded.
 4. The method of claim 2, wherein a maximum valueof the number syntax element is determined as a number of tiles in thepicture multiplied by a number of the rows of coding tree units minusone when two or more tiles are present in the picture and the rows ofcoding tree units are parallel decoded.
 5. A video decoding method,performed by a decoding apparatus, comprising: obtaining entry pointinformation specifying an entry point of a substream for a picture froma bitstream; and reconstructing the picture based on the entry pointinformation, wherein the entry point information include a number syntaxelement representing a number of offset syntax elements in a sliceheader, wherein the entry point information includes an offset syntaxelement when the number of the offset syntax elements is larger than 0,wherein the offset syntax element represents an entry point offsetbetween two entry points, wherein the entry point information includes alength syntax element when the number of the offset syntax elements islarger than 0, wherein the length syntax element represents a bitslength of the offset syntax element, wherein the offset syntax elementrepresents the number of bytes between the two entry points, wherein avalue of the length syntax element plus one corresponds to the bitslength of the offset syntax element, wherein a value of the numbersyntax element corresponds to the number of offset syntax elements inthe slice header, and wherein the entry point information is configuredin the slice header.
 6. The method of claim 5, wherein the number of theoffset syntax elements is determined based on whether two or more tilesare present in the picture and whether rows of coding tree units in thepicture are parallel decoded.
 7. The method of claim 6, wherein amaximum value of the number syntax element is determined as a number ofthe rows of coding tree units in the picture minus one when two or moretiles are not present in the picture and the rows of coding tree unitsare parallel decoded.
 8. The method of claim 6, wherein a maximum valueof the number syntax element is determined as a number of tiles in thepicture multiplied by a number of the rows of coding tree units minusone when two or more tiles are present in the picture and the rows ofcoding tree units are parallel decoded.
 9. A non-transitory computerreadable storage medium storing encoded information causing a videodecoding apparatus to perform operations comprising: obtaining entrypoint information specifying an entry point of a substream for a picturefrom the encoded information; and reconstructing the picture based onthe entry point information, wherein the entry point information includea number syntax element representing a number of offset syntax elementsin a slice header, wherein the entry point information includes anoffset syntax element when the number of the offset syntax elements islarger than 0, wherein the offset syntax element represents an entrypoint offset between two entry points, wherein the entry pointinformation includes a length syntax element when the number of theoffset syntax elements is larger than 0, wherein the offset syntaxelement represents the number of bytes between the two entry points,wherein the length syntax element represents a bits length of the offsetsyntax element, wherein a value of the length syntax element plus onecorresponds to the bits length of the offset syntax element, wherein avalue of the number syntax element corresponds to the number of offsetsyntax elements in the slice header, and wherein the entry pointinformation is configured in the slice header.